HOW DOES MY RUNNING AFFECT IT?

While exercise burns calories, it’s the results – building muscle mass – that really make a difference in terms of your metabolism. ‘The amount of muscle mass you have is the biggest factor determining your BMR,’ says Professor Grant Brinkworth, principal research scientist at CSIRO, Australia’s national science agency.

‘BMR contributes the greatest proportion of TDEE, so adopting strategies that improve it will have the biggest impact on increasing energy metabolism.’ Your body has to work harder to maintain muscle tissue when you’re at rest than it does fat tissue.

You naturally begin to lose muscle mass after the age of 30, but you can prevent and even reverse some of that loss by doing regular resistance workouts, embracing strength-building hill repeats and eating enough protein.

Better yet: all movement will hike your metabolism by varying degrees, but high-intensity interval training keeps it elevated for up to 48 hours after you finish your session. If you do an intense workout, where your heart rate is between 85 and 90 per cent of its maximum, your body has to work hard to replenish glycogen and rebuild muscle proteins damaged during exercise to return your body to its resting state. This is called excess post-exercise oxygen consumption (EPOC), but it’s no reason to skip your strength work in favour of an interval session: ‘Weights workouts can produce a good EPOC effect, especially if done for 45 minutes to an hour,’ explains exercise physiologist Drew Harrisberg.

‘Of course, it’s worth noting that building muscle requires more fuel in the first place,’ adds Miller. ‘This is part of the reason why, if you undereat in terms of overall calories for the day, you won’t build muscle anywhere near as fast as you will if you fuel properly for your training, even if genetics are on your side.’